Apparatus for indicating liquid level



Oct. 21, 1952 w. F. HUNTER ETAL 2,614,427

APPARATUS FOR INDICATING LIQUID LEVEL Filed April 10, 1951 WALKER F. HUN YER E'IMR W JENSEN ,INVENTORS A TTORNEYS Patented Oct. 21, 1952 APPARATUS FOR INDICATING LIQUID LEVEL Walker F. Hunter and Einar W. Jensen, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application April 10, 1951, Serial No. 220,295

1 Claim. 1

This invention relates to apparatus for measuring the level of a liquid in an enclosed tank, and more particularly to apparatus which is especially adaptable for determining within a relatively narrow vertical range, the level in a tank, or. similar container, of highly viscous solutions such as cellulose organic ester solutions and the like.

With such highly viscous solutions the usual types of level gauges such as floats, gauge glasses, and certain pressure measuring devices in certain instances cannot be employed effectively due to the physical properties of the liquid such as viscosity and density variation. Because of the highly volatile and in some instances inflammable solvents employed with cellulose organic acid ester solutions, electrical type level controls are undesirable since there is always a possibility that an explosive air-solvent mixture might exist in the presence of the electrical control mechanism and be exploded by electric arcs produced by the mechanism. After some investigation we have found that a level indicating device which is pneumatically operable is quite satisfactory for employment in measuring the level of various liquids and solutions.

An object, therefore, for the present inven-- tion is an apparatus forindicating the level of a liquid in an enclosed tank within a desired vertical range of levels.

Another object of the invention is a liquid level indicating apparatus which will operate effectively with highly viscous solutions, such as cellulose organic acid ester solutions.

Still another object of the invention is a simple, inexpensive and safe level indicating device for use in connection with highly viscous and/or inflammable solutions.

Other objects will appear hereinafter.

The invention will be understood from the following detailed description and related drawing having parts both in section or broken away. In the drawing, which is not to scale, the tank normally being much larger than the level indicating device, tank made, for example, of metal such as stainless steel is shown containing a viscous solution 21, the level of which is to be indicated on gauge 24 when it is within a certain vertical range of levels in the tank ID. The solution 21 may be introduced into tank l0 through pipe II which has valve l2 therein and it may be withdrawn from the bottom of the tank through pipe l3 which has valve l4 therein. The tank may be, for example, a place of storage for a cellulose ester solution which has been formed elsewhere.

As evident in the drawing the upper left side of the tank I!) has an opening therein which is closed tightly by a flexible metal diaphragm I8 which is tensioned radially so it forms a vertical plane and, therefore, separates the liquid 21 from a chamber 20 formed by an encasing member ll. A conduit It connects chamber 20 with conduitl5 which in turn is connected with tank l0. Conduit I5 is vented to the air at a point not shown, which is remote fromthe tank.

An air nozzle 19 at the end of pipe 22 is positioned within chamber 20 to discharge cornpressed air against diaphragm I8 at its approximate center point. As shown in the drawing the compressed air impinges on the diaphragm l8 substantially at a right angle. An adjusting screw 2| engaging and passing through member ll contacts pipe 22 adjacent its nozzle and is adapted to regulate the distance of the nozzle l9 from the diaphragm l8. Compressed air from a source, not shown, flows through pipe 26, restriction 25 to aforesaid pipe 22. Pressure gauge 24 is connected to pipe 22 through pipe 23. The nozzle I9 is first adjusted by screw 2l to a distance from the diaphragm 18 so that air striking the diaphragm will produce a constant back pressure, at some desired point in the range of 5 to 10 p. s. i. g. between the restriction 25 and nozzle l9 when there is no liquid 2! in contact with the diaphragm l8. Compressed air at about 20 p. s. i. g. is supplied to the restriction 25. Pressures of 15 to 30 p. s. i. g. could be employed and the selected pressure should be substantially constant. The nozzle back pressure is, of course, measured by gauge 24.

The apparatus operates as follows: With no liquid in contact with the diaphragm I 8, and air flowing out of the nozzle l9 against diaphragm IS, the nozzle back pressure is at a desired value, for example, 7 p. s. i. g. As the liquid level rises over the face of the diaphragm is the diaphragm is deflected outwardly (to the left) thereby tending to seal off the opening between the nozzle l9 and diaphragm 18.. This action results in an increase in nozzle back pressure which is measured by gauge 24. By calibration, the nozzle back pressure as shown by gauge 24 can be related to the height of the liquid within vertical liquid height corresponding to the height of the diaphragm It.

Any change in pressure in the gas or vapor space above the liquid would aiiect the response of this apparatus unless the pressure in chamber 20 were the same, therefore, for any enclosed tank, the nozzle must be enclosedby mem- 3 her I! which is vented through pipe [8 and 15 to the gas space above the liquid in tank I. This connection through pipes l5 and I6 cancels any change in gas or vapor pressure in either chamber 20 or tank In. Pipes l6 and [5 of course also permit the compressed air flowing from nozzle l9 tofiow out of chamber 20. This device will operate efiectively with highly viscous cellulose ester solutions of the order of 60,000 to 100,000 c. p. s. such as those describedi-n U. Si Patent 2,541,012 of February 13, 1951, although it is equally effective with liquids oi'less'viscosity" and could be employed even i'orm'easuring'the height of water in such a tank;

It will be evident that our liquid level device will not indicate the amount of liquid in. the tank when its level is below the level. range measurable by the diaphragm although indicating that the tank is not full. However, this is immaterial for some purposes and we have found that our" simple and relatively inexpensive level gauge is desirable for various applications.

We claim:

Apparatus for measuring liquid-level in a tank comprising in: combination atame containing liquid, the changing level of which is to be-measured, an aperture inthe side ofthe tan-k a flexible diaphragm positionedover the aperture and adapted to contact the liquiclover a certain vertical level range and to move inwardly and outwardly by variance in liquid ressure produced by changes in liquid level in the tan-k 4 within said level range, a casing enclosing the opposite side of the diaphragm and forming a chamber therearound, a compressed air pipe having a nozzle extending into the chamber adapted to discharge air onto the approximate center point ofthe diaphragm, a restrictirm in the pipe outside the chamber, a pressure gauge attached to the pipe adjacent the restriction and between the restriction and the nozzle adapted to measure the. change inlback pressure of the air flowing through the nozzle as the movement of the diaphragm varies the flow of air through the nozzle-in direct ratio to the change in fluid level over'sa'i'ci range, and means for venting gases in said chamber and tank to the atmosphere.

WALKER F. HUNTER.

EINAR W. JENSEN.

REFERENCES CITED The following references are of record the file of this patent:

UNITED STATES PATENTS; 

